1. Field of the Invention
The present invention relates to a double-sided reclining apparatus, and more particularly to a rotary-cam type double-sided reclining apparatus in which a pair of reclining devices, mechanically linked to each other, are attached to both sides of an automotive seat, and the locking and unlocking action of each of the reclining device is made by way of a rotary motion of the rotary cam mechanically linked to a reclining lever to ensure the angular adjustment of a seat back relative to a seat cushion.
2. Description of the Prior Art
On earlier model cars, a double-sided seat reclining apparatus is ordinarily used for enhancing a holding performance of a seat back adjusted at a desired angular position and for providing a long-life reclining device. Generally, each reclining device constructing the double-sided reclining apparatus is comprised of a rotary-cam type reclining device which has a base fixedly connected to seat cushion, an arm fixedly connected to a seat back and rotatably supported by the base, at least one toothed block slidably guided in the two opposing parallel side walls in the base, a reclining lever, and a rotary cam which is usually fixedly connected to the pivot shaft of the reclining lever, and which acts to mesh or unmesh the toothed block with or from the inner toothed portion of the arm by way of rotation of the rotary cam. Such conventional double-sided reclining apparatus have been disclosed in Japanese Patent Provisional Publication Nos. 9-28496 and 9-131237, assigned to the assignee of the present invention. The Japanese Patent Provisional Publication No. 9-28496 corresponds to U.S. Pat. No. 5,727,846 issued Mar. 17, 1998 to Tomonori Yoshida. The double-sided reclining apparatus disclosed in the Japanese Patent Provisional Publication No. 9-28496 is characterized by the difference between a cam profile of a rotary cam included in a locking/unlocking mechanism of a first reclining device (corresponding to an outside reclining device employing a reclining-lever handle) and a cam profile of a rotary cam included in a locking/unlocking mechanism of a second reclining device (corresponding to an inside reclining device not employing a reclining-lever handle), thereby permitting a mechanical phase-lead of the inside reclining device with respect to the outside reclining device. This mechanical phase-lead provides a stable reclining action, while insuring a correct feel of the reclining-lever action. Japanese Patent Second Publication No. 63-65327 has disclosed a rotary-cam type reclining device having a rotary cam and a plurality of toothed blocks radially slidable with respect to the pivot shaft of the reclining lever to ensure locking/unlocking action of the reclining device at a desirable adjusted position of the seat back. The Japanese Patent Second Publication No. 63-65327 teaches the provision of a specified clearance between the toothed block and the associated two opposing parallel guiding side walls to ensure a smooth locking/unlocking action of the reclining device, and simultaneously teaches the provision of at least a specified clearance between the cam and the arm to absorb the dimensional error between the rotational axis of the rotary cam fixed to the pivot shaft of the reclining lever and the rotational axis of the arm whose central bore slidably fitted onto the outer periphery of the somewhat axially-extending boss-like portion of the rotary cam. However, in the reclining apparatus disclosed in the Japanese Patent Second Publication No. 63-65327, the boss-like portion of the cam is fixedly connected to the pivot shaft of the reclining lever for example by way of welding, thus resulting in a slight eccentricity between the rotational axis of the cam and the central axis of the pivot shaft. This slight eccentricity would result in undesirable mechanical phase-mismatching between the meshing/unmeshing mechanisms employed in the pair of reclining devices.
Japanese Patent Provisional Publication No. 7-136032 teaches the provision of a clearance between the width-across flatted shaft portion of the pivot shaft and the width-across flatted hole portion of the cam to permit the slight radial motion of the cam in the sliding direction of the toothed block, thus ensuring sufficient cam-connection between the cam-profile surface of the rotary cam and the cam-contour surface of the toothed block with one cam-connection point. However, if the dimensional error exists in a direction perpendicular to the sliding direction, it is impossible to accurately self-align or match the rotational axis of the rotary cam with respect to the center axis of the pivot shaft. Such a dimensional error may produce inadequate cam-connection between the cam-profile surface of the rotary cam and the cam-contour surface of the toothed block, and prevent the toothed portion of the toothed block from being smoothly brought into meshed-engagement with the inner toothed portion of the arm.